According to my sources, a D10 would have had a 26mm Amal 626 Concentric, with a 150 main jet, a 25 pilot, a no 3 slide, a .105 needle jet and the needle in position 2. 

Fisambard said
Weren’t the early models Monobloc?  

Possibly. My references only list the above, but they also state that the Concentric was introduced in the 1967 model year, so September 66 onwards. The D10, particularly the 3-speed, was a bit of an interim model, with some hangovers from the preceding D7, but not all the improvements the D14/4 saw. I’m afraid I can only offer the information in my book, as my direct experience is with the D1/3/5 machines, and with the engines of the D14/4 and D175.